Induction furnace



July 1, 1930. P. H. BRAcE INDUCTION FURNACE 2 Shania-sheet 1 Filed Aug.14. 1929 INVENTOR Porer/fBrace.

ATTORNEY 2 Sheets-Sheet 2 l N v E N To R Porer/ Brace.

TTORNEY Patented July 1, 1930 UNITED STATES PATENT OFFICE PORTER H.BRACE, 0F FOREST HILLS, PENNSYLVANIA, `ASSIGNOR T0 WESTINGHOUSE ELECTRIC& MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA INDUCTION FURNACEApplication led August 14, 1929. Serial No. 385,764.

My invention relates to electric furnaces and particularly to electricinduction furnaces of relatively large size.

An obj ect of my invention is to provide an induction furnace that shallembody means for establishing a plurality of substantially separatesecondary electric circuits, whereby the length of effective currentpath and of energy input is increased.

Another object of my invention is to provide a crucible for asurrounded-pool-type induction furnace that shall embody a plurality ofrefractory walls disposed in substantially radial positions andcooperating with the crucible wall to divide material located in thecrucible into a number of substantially separate sections. i

Another object of my invention is to provide the refractory dividing orseparating walls with metallic strengthening and cooling meansinterfitting therewith and substantially covered thereby.

In practicing my invention, I provide a refractory crucible of thesurrounded-pool type with a plurality of intermediate refractory wallsdisposed in substantially axial and'radial positions to cooperate withthe crucible to provide a plurality of substantially similar andsubstantially separated sections within the crucible distributedperipherally thereof `to increase the effective length of the path ofthe secondary current induced in the material to be melted. Means arerovided in one or more of the Walls to permit of emptying the crucibleat one time.

In the drawings,

Figure 1 is a top plan View of an electric induction furnace embodyingmy invention,

a portion of the cover being shown in place;

Fig. 2 is a vertical section taken on the line II-II of Fig. 1;

Fig. 3 is a schematic top plan view of a modified form of deviceembodying my invention;

Fig. 4 is a schematic top plan View of a further modification;

Fig. 5 is a top plan View of a still further modification of a deviceembodying my invention, and

Fig. 6 is a view, in lateral vertical section, taken on the line VI-VIof Fig. 5.

Referring more particularly to Figs. 1 and 2 of the drawings, I havethere shown an outer metal casing 11 which may be provided with shortshafts or trunnions 12 and 13 to permit of tilting the furnace. Abuiltup lining or crucible 14 is provided as may be necessary ordesirable in case of furnaces of relatively large capacity. Immediatelysurrounding the crucible 14, is a layer 16 of granular refractorymaterial which is maintained in its proper operative position by a casin17 of electric-insulating material and of su stantially the same generalshape as the crucible.

An energizing coil 18 includes a plurality of turns of anelectric-conducting member and a fluid-conducting member shown insection in Fig. 2 of the drawings. Granular electric and heat-insulatingmaterial 19 is located Within the casing 11 and is adapted to supportthe coil 18 and the members 17 and 14 and the granular material 16. Acover 20 may be provided at the top of the furnace structure.

A plurality of axially and radially-disposed refractory walls 21, 22 and23 are symmetrically spaced peripherady within the.

crucible 14 and extend from substantially the 80 center or axis of thecrucible to the crucible wall itself and are interfitted therewith,substantially as shown in Fig. 1 of the drawings,

Figs. 3 and 4 show, respectively, modifications of the idea ofsubdividing the material to be located in the crucible 14, Fig. 1showing a lining or crucible 26 having a plurality of radially extendingwalls 27, also of refractory material, located therein but not engagingeach other at their inner ends. In this case, the sections of materialwithin the crucible being heated Will not be entirely separated.

Fig. 4 shows a substantially circular lining or crucible 28 of arefractory material having located therein a plurality of radiallyextending refractory walls 29, the outer ends of which interfit with thewall 28, and a substantially solid central core member 31 also ofrefractory material. In this case, the respective ICO sections withinthe crucible 28 will be entirely separate from each other. i

Referring more particularly to Flgs. 5 and 6 of the drawings, I havethere illustrated an rial 37 and a shroud 38 of electric-insulatinmaterial are located between the crucible an the energizing coil.Granular material 39 is located between the shroud 38 and the casing 32and has electric and heat-insulating characteristics. A cover 40 may beprovided.

A pluralitty of spaced and substantially radial refractory wa ls 41, 42and 43 are provided, the ends of which interfit with the walls of thecrucible 33.

The respective walls 41 to 43, inclusive, are built up of a plurality ofrelatively thin bricks or blocks of refractory material adapted towithstand the chemical action of the materal being melted and also therelatively high temperature of the molten material.

As these walls provide paths for flux which will not be effective inheatin the material, it is desirable that the thic ess of these walls bereduced as much as possible, consistent with the necessar mechanicalstrength. I, therefore, provi e an interlitting metal structure for eachof these walls which, as shown more particularly in Fig. 6 of thedrawings, includes a bottom ortion 44 of metal upon which the wall isbuilt as well as upwardly extendin portions 46 between which the bricksor b ocks constituting the walls 41, 42 and 43 are fitted. The upper endportion of each of the members 46 may be headed over, as shown in Fig. 6in order to maintain the bricks or blocks of the respective walls intheir proper operative positions on the portions 44.

Means for cooling the respective walls 4l to 43, and, more particularly,the metal bases 44, are provided in the form of conduits 47 which extendoutwardl through suitable openings in the wall of t e casing 32 and areconnected to a source of supply of a cooling fluid, in the manner showngenerally in Fig. 5 of the drawings.

In the case of relatively large furnaces operating at commercialfrequencies, such as 25 to cycles, as well as in small furnaces, of thesurrounded-po@ t pe, operating at higher frequencies, it usuallyyhappens that the current-carrying zone of the charge is of relativelysmall depth radially, as compared to the diameter of the charge. Thismeans that only a relatively small portion of the total volumeundesirable electrical an mechanical complications which limit thepermissible amount of energy input and, in the case of large furnaces,it may happen that this energy input is undesirably low, when related tothe metalholding capacity of the furnace chamber.

Tht provision of a plurality of refractory walls within a lining orcrucible extending axially thereof in one direction and radially thereofin another direction, ensures substantially separate material-holdingcompartments, so that the original circumferential zone of the secondarycurrent is replaced by a system including a plurality of current zoneswhich conform, 1n a general way, to the outer wall of the meltingchamber or crucible and the corresponding surfaces of the partitionwalls.

By dividing a substantially circular furnace chamber into three smallerchambers, as shown in Fig. 1 of the drawings, the total length ofeffective current zone is approximately doubled and the ower intake ofthe furnace with a given coi and with a predetermined current traversingsaid coil is correspondingly increased. This has the result that boththe efliciency and the power factor of a furnace of my new type areimproved, the efficiency being particularly improved because the energytransfer to, and received by, the material being heated has beensubstanf tially doubled without increasing the amount of energy ex endedin the coil or without increasing the lieat loss from the material inthe crucible and from the crucible itself.

The im rovement in the power factor will be depen ent upon the thicknessof the refractory-partitions for the reason that idle ma netic fluxpasses through the space occupie by these non-conducting walls and,hence, I prefer, wherever possible, to use the structure shown in Figs.5 and 6 which not onl cools the refractory artitions but also ena les meto make them o a minimum effective thickness.

Openings are provided in the partitions at spaced points, such as thejunction of each partition with the outer periphery of the furnacechamber, these beinnr shown by numeral 51 in Fig. 2 of the drawing andby numeral 52 in Fig. 6 of the drawing. This permits of emptyingsubstantially all of the molten material in a crucible at any one timeand these openings have the further effect of diminishing the effectivethickness of the partition walls, because the metal filling theperforations in the walls obstructs passage of idle ux through theaxial-space volumes occupied by the partitions and, by so doing, itabsorbs ener y. I have, thmerefore, shown a pluraliy o such openings, itbeing understood fil that the number of such openings may be such as maybe found suitable or desirable in accordance with the above notedconsiderations.

The use of interfitting metallic members with the refractory partitionsprovides a much stronger partition than would otherwise be the case, andthe use of fluid cooling means aids in lengthening the life of thesepartitions.

Various modifications may be made in the device embodying my inventionWithout departing from the spirit and scope thereof, and I desire,therefore, that only such limitations shall be placed thereon as areimposed by the l prior art or are set forth in the appended claims.

I claim as my invention:

1. In an electric heating device including a crucible and a helicalenergizing coil surrounding it, means in said Crucible cooperatingtherewith to provide a plurality of substantially separate secondaryelectric circuits in a mass of material located in said crucible.

2. In an induction furnace of the surrounded-pool type having arefractory lining and a helically-wound energizing coil, refractorymeans in said lining cooperating therewith to largely increase the totallength of effective current path in material to be heated therein.

.3. In an induction furnace of the surrounded-pool type having arefractory Crucible and a helically-Wound energizing Coil, a pluralityof refractory Walls connecting peripherally spaced points of therefractory cru- Cible to provide a plurality of substantially separatesecondary electric circuits in a mass of material located in saidCrucible.

4. In an induction furnace of the surroundecl-pool type having arefractory Crucible and a helically Wound energizing coil, a pluralityof refractory Walls disposed in substantially radial and axial positionsin the crucible and joined therewith to establish a plurality ofsubstantially separate secondary electric Circuits in a mass of materiallocated in said cru- Cible.

5. In an induction furnace, in combination, a pot-type Crucible ofrefractory material, a plurality of refractory Walls therein cooperatingwith the Crucible to provide aplurality of similar, substantiallyseparate and uniformly spaced furnace sections for receiving material tobe heated, and a single energizing coil surrounding the Crucible.

6. In an induction furnace, a single helically-Wound energizing coil anda plurality of substantially separate and similar crucible sectionslocated Within the coil, extending peripherally of the axis thereof andenergized simultaneously thereby.

7. In an induction furnace, in combination, a lining of refractorymaterial, a plurality of refractory Walls therein cooperating with thelining to provide a plurality of similar, substantially separate anduniformly spaced furnace sections for receiving material to be heated, asingle energizing coil surrounding the lining, and means in certain ofsaid refractory walls for effecting emptying of all of said furnacesections at one time and for reducing the stray flux traversing saidrefractory Walls 8. In an induction furnace of the surrounded-pool typehaving a refractory lining and a helically Wound energizing coiltherearound, a plurality of refractory Walls radially disposed in thelining and joined thereto to establish a plurality of substantiallyseparate sec,- ondary electric circuits in a mass of material located insaid lining, means in said refractory Walls for strengthening the same,and means for artificially cooling said strengthening means.

9. In an induction furnace, a single helically-Wound energizing Coil, arefractory lining, of pot-type, Within said energizing coil, andrefractory means in said lining to cooperate therewith to increase theenergy transfer from the energizing coil to material located in thelining relatively to that transferred inthe absence of said means.

10. In an induction furnace of the surrounded-pool type having arefractory lining and a helically Wound energizing coil therearound, aplurality of substantially radial and l axial refractory Wallscooperating with therefractory lining to establish a plurality ofsubstantially separate secondary electric circuits in a mass of materiallocated in the lining, said circuits being symmetrically spacedperipherally of the axis of the coil and the lin- Il. In an inductionfurnace,l in combination, a pot-type crucible of refractory material, apluralityof refractory walls therein cooperating with the Crucible toprovide a plurality of similar, substantially separate anduniformlyvspaced furnace sections for receiving material to be heated, asingle energizing coil surrounding the Crucible, a

metal member at the bottom of each refrac-

